Method for separating metal contaminants from organic polymers

Abstract

A method for separating metal residues from a polymer wherein a solution or suspension of said polymer is contacted with an aqueous solution containing one or more inorganic acids in the presence of a monocarboxylic acid containing from about 6 to about 20 carbon atoms. The polymer solution or suspension will be contacted with an oxidizing agent either prior to or simultaneously with the contacting with the aqueous inorganic acid solution. The inorganic acid is, preferably, a mineral acid and the monocarboxylic acid is preferably a branched chain alkanoic acid having from about 6 to about 10 carbon atoms. When a monocarboxylic acid is used in combination with the inorganic acid, the amount of metal removed from the polymer is increased and the amount of the aqueous phase containing ionized metal entrained in the organic phase is sugnificantly reduced.

Having thus described and illustrated this invention, what is claimed is: 
     
       1. A method for separating metals from a polymer comprising the steps of: (a) contacting a solution or suspension of a polymer and metals introduced as a hydrogenation catalyst in an organic media with an oxidizing agent;   (b) contacting said solution or suspension of said polymer and said metals with an aqueous solution of an inorganic acid in the presence of a monocarboxylic acid having from about 6 to about 20 carbon atoms; and   (c) recovering a polymer product having a reduced amount of metal therein.   
     
     
       2. The method of claim 1 wherein said inorganic acid is a mineral acid. 
     
     
       3. The method of claim 2 wherein said mineral acid is sulfuric acid. 
     
     
       4. The method of claim 1 wherein said monocarboxylic acid is a branched chained alkanoic acid having from about 6 to about 10 carbon atoms. 
     
     
       5. The method of claim 1 wherein steps (a) and (b) are accomplished simultaneously. 
     
     
       6. The method of claim 1 wherein step (b) is accomplished in a plurality of steps. 
     
     
       7. The method of claim 1 wherein said monocarboxylic acid is significantly more soluble in an organic media than in an inorganic media. 
     
     
       8. The method of claim 1 wherein step (a) is accomplished at a temperature within the range from about 50° to about 100° C., a pressure within the range from about 0 to about 100 psig and at a nominal holding time within the range from about 10 to about 90 minutes. 
     
     
       9. The method of claim 1 wherein step (b) is accomplished at a temperature within the range from about 50° to about 100° C., a pressure within the range from about 0 to about 100 psig and at a nominal holding time within the range from about 10 to about 90 minutes. 
     
     
       10. The method of claim 1 wherein said polymer is a block copolymer comprising at least one polymeric block containing predominantly monoalkenyl aromatic hydrocarbon monomer units and at least one polymeric block containing predominantly hydrogenated, conjugated diolefin monomer units. 
     
     
       11. The method of claim 10 wherein said polymer is in solution. 
     
     
       12. The method of claim 11 wherein a sufficient amount of aqueous solution containing the inorganic acid will be used to provide from about 1 to about 10 times the stoichiometric amount of inorganic acid required to react with all of the metals contained in the polymer solution. 
     
     
       13. The process of claim 12 wherein said monocarboxylic acid is ethylhexanoic acid.